Sample applicator for point of care device

ABSTRACT

The invention relates to a microfluidic system for processing biological samples comprising a transfer pipette; a platform adapted to provide at least one receiving chamber and configured to receive said transfer pipette, and a distal output chamber wherein a biological sample from the transfer pipette is dispensed into the output chamber when a centrifugal force is applied.

CROSS REFERENCE TO RELATED APPLICATIONS

This is the national phase under 35 U.S.C. § 371 of InternationalApplication No. PCT/EP2015/060216, filed on May 8, 2015, which claimspriority to and the benefit of European Patent Application No.14167545.4, filed on May 8, 2014 and U.S. Patent Application No.61/990,611, filed on May 8, 2014, the entire disclosures of each ofwhich are incorporated by reference herein.

FIELD

The disclosure relates to a sample applicator apparatus, system andmethod, for use in a point of care diagnostic device for application ofliquid samples.

BACKGROUND

Manual processing to determine the cellular/biological content ofvarious types of biological samples, and in particular samples thatcontain living cells, is cost-prohibitive in many applications and isalso prone to errors. Automation is also cost-prohibitive in manyapplications, and is inappropriate as currently practiced—using, forexample, liquid handling robots—for applications such as point-of-careor doctor's office analysis.

There have been many recent advances in point-of-care diagnostic assaysystems based on centrifugal microfluidic technologies. Such systemstypically comprise i) a centrifugal microfluidic cartridge with reagentstorage and sample processing methods, and ii) related device readersfor interrogation of samples processed on such centrifugal microfluidiccartridges. However, there is an unmet need to provide a simple methodof biological sample application, compared with current point-of-carecentrifugal microfluidic based diagnostic assay systems, that i) is lessprone to user error, ii) minimises biohazard and aerosol contaminationrisk, iii) removes the requirement of cartridge cleaning, iv) simplifiesuser workflow protocols v) simplifies cartridge manufacture and cost,and vi) integrates user fail-safe mechanisms.

Existing centrifugal-based point-of-care diagnostic assay systemstypically use either i) an external transfer pipette for application ofliquid samples, or ii) an inlet capillary port integrated on thecartridge, whereby the sample is applied directly onto the cartridge.While the cartridges associated with both system approaches can performa variety of integrated sample preparation and assay tests—such aslateral flow assays, electrochemical assays, etc.—their sampleapplication methods do not address the aforementioned unmet need.

Consider the first case of an external transfer pipette. In thisinstance, a biological sample is applied to the transfer pipette throughcapillary action upon contact by the pipette's tip with the sample. Thepipette tip is then typically inserted into the centrifugal cartridge'sinlet chamber which is situated close to the cartridge's centre. Thesample is dispensed (or transferred), for example, through either anintegrated air-displacement piston within the pipette or squeezing of arubber bulb on top of the pipette, depending on the pipette's design.This sample application method suffers the risk of aerosol or biohazardcontamination once the centrifugal cartridge is spun. While integratingan absorbent material into the cartridge's inlet chamber reduces thisrisk, it does not eliminate it, and further complicates the cartridge'smanufacturing process. Covering the inlet chamber with a physicalbarrier increases cost and biohazard risk, and adds user workflow steps,thereby increasing user training requirements.

Consider the second case of an integrated inlet capillary port. In thisinstance, a biological sample is applied directly onto a cartridge'sinlet capillary port from, for the example of whole blood, a patient'slanced finger. The inlet capillary port typically protrudes somewhatfrom the cartridge to facilitate both user operation and sampleapplication. Such methods typically require advanced user training aspositioning the inlet capillary port to contact the patient's finger canbe problematic and lead to unsuccessful or poor quality application.Such integrated inlet capillary ports complicate the cartridge'smanufacturing process adding to cost and reducing production yield. Theyalso require the application of a physical barrier, as in the previouscase, to minimise biohazard and aerosol contamination.

There are a numerous examples in the art which illustrate the firstcase. Examples include U.S. Pat. No. 4,898,832 (Boehringer Mannheim), JP2008 032695 (Matsushita) U.S. Pat. No. 5,061,381 (Abaxis) and U.S. Pat.No. 6,143,248 (Gamera) which describe various sample processing methods,but all use external transfer pipettes to load the sample.

One such example of the second case in the art is US2009/205447(Panasonic) which describes a system for transferring a sample liquiddispensed as a drop on an inlet port. The inlet port is formed toprotrude in a direction away from the chamber, a recessed section isformed around the injection port, and the inlet port is arranged on theside of a rotating axis centre so that centrifugal force, upon itsrotation, transfers the sample to said chamber. A hinged cover mechanismprevents biohazard and aerosol contamination.

It is therefore an object to provide a low-cost, simple sampleapplication apparatus and method to address at least one problem knownin the art.

SUMMARY

According to the invention there is provided, as set out in the appendedclaims, a microfluidic system for applying biological samplescomprising:

-   -   a transfer pipette;    -   a rotary motor;    -   a means for controlling said motor; and    -   a platform coupled to the rotary motor and adapted to provide at        least one chamber to receive said transfer pipette, and an        integrated output chamber wherein the sample is dispensed.

In one embodiment there is provided a microfluidic system for processingbiological samples comprising:

-   -   a transfer pipette;    -   a platform adapted to provide at least one receiving chamber and        configured to receive said transfer pipette, and a distal output        chamber wherein a biological sample from the transfer pipette is        dispensed into the output chamber when a force is applied.

In one embodiment the meniscus of the said applied biological sample atthe transfer pipette tip is radially distal from the opposite meniscuswithin the said transfer pipette.

In one embodiment the transfer pipette is a capillary pipette comprisingan air vent.

In one embodiment the radial distance of the sample meniscus proximateto the pipette tip is larger than the radial distance of the samplemeniscus distal from the tip.

In one embodiment the transfer pipette comprises an air vent to ensuretransfer of air during the biological sample application to, anddispensing from, the transfer pipette.

In one embodiment the force applied is a centrifugal force caused byrotation of the platform.

In one embodiment the said transfer pipette comprises a single-uselocking mechanism adapted to prevent removal during rotation by therotary motor.

In one embodiment the transfer pipette comprises a fluidic barrier suchthat the meniscus of the said applied biological sample at the transferpipette tip is radially distal from the opposite meniscus within thesaid transfer pipette.

In one embodiment there is provided a fluidic barrier within thetransfer pipette prevents the escape of biological sample through theopposite end of the transfer pipette.

In one embodiment the biological sample is replaced with an otherwiseconstituted sample of liquid form.

In another embodiment there is provided a transfer pipette for use witha microfluidic system to process biological samples comprising:

a channel to collect and store the biological sample; and

-   -   an air vent to ensure transfer of air during the biological        sample application to,    -   and dispensing from, the transfer pipette to the microfluidic        system when a force is applied.

In a further embodiment there is provided method of processingbiological samples in a microfluidic comprising the steps of:

-   -   coupling a transfer pipette to a platform; and    -   rotating the platform such that the biological sample from the        transfer pipette is dispensed into an output chamber of the        platform.

While this invention relates and applies to a myriad biological samples,such as whole blood, saliva, serum, sweat, etc., the specific embodimentdescribed herein concentrates on the sampling of whole blood from apatient's finger.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention will be more clearly understood from the followingdescription of an embodiment thereof, given by way of example only, withreference to the accompanying drawings, in which:

FIG. 1 illustrates a transfer pipette inserted into a receiving chamberof a centrifugal cartridge according to one embodiment of the invention;

FIG. 2 illustrates a whole blood sample from a lanced finger beingapplied to the removed transfer pipette according to one embodiment ofthe invention; and

FIG. 3 illustrates schematically the transfer pipette and discstructures which provide the mechanism to dispense the applied sampleinto an integrated output chamber.

DETAILED DESCRIPTION OF THE INVENTION

Herein is described a sample application method comprising a transferpipette wherein a sample is applied to same through capillary action,said pipette is inserted into a receiving chamber on a centrifugalcartridge, with the pipette designed to ensure the sample is dispensedinto an integrated output chamber.

FIG. 1 illustrates a high-level sample applicator and cartridgeconstruction comprising a centrifugal microfluidic cartridge 101 withcentre 102, which is coupled to a rotary motor (not shown), andcircumference 103 drawn with two segments removed, according to oneembodiment of the invention. The sample applicator comprises a transferpipette with handle 104 attached to its sample transfer body 105. FIG. 1illustrates the transfer pipette inserted within the cartridge, withouta sample applied. Later illustrations describe geometrical relationshipsand the function of the integrated output chamber 106 with an outletchannel 107. An air vent 108 in the transfer pipette's handle, enablesair displacement within the transfer pipette to allow sample applicationand dispensing, through capillary and centrifugal forces, respectively.A fluidic barrier 109 minimises the leakage of applied sample to theoutside environment

FIG. 2 illustrates a typical protocol by which the sample is firstapplied to the transfer pipette and further details the high-levelcartridge structures. Herein is shown a cartridge 201 comprising acentre 202, which is coupled to a rotary motor (not shown), and outputchamber 203 with associated outlet channel 204, as already shown inFIG. 1. The transfer pipette 205 is removed from the cartridge, therebyshowing the receiving chamber 206 on the cartridge, connected to theoutput chamber which is distal from the receiving chamber. The air vent207 within the transfer pipette and associated fluidic barrier 208 areas previously described. The figure illustrates the use case for afinger-prick of whole blood, whereby a finger 209 upon being lanced,using a procedure known to those skilled in the art, produces a wholeblood sample 210 on the surface of the finger. It will be appreciatedthat the transfer pipette can receive a sample by any contact with thesample and not necessarily from the surface of the finger. Upon contactwith the transfer pipette, the blood sample begins to fill by capillaryaction towards the pipette head up to a point which shall be defined asthe trailing sample meniscus 211.

FIG. 3 illustrates the detailed workings of this invention. As before,the cartridge 301 comprises centre 302, which is coupled to a rotarymotor (not shown). The transfer pipette 303 is re-inserted into thecartridge via the receiving chamber previously illustrated in FIG. 2. Afirst notional centreline ℄1 is shown intersecting the cartridge centreand scribed perpendicular to the receiving chamber. A second notionalcentreline ℄2 is shown perpendicular to ℄1 and projects along the centreaxis of the transfer pipette. The transfer pipette is shown with appliedsample 304 filled between the trailing sample meniscus 305 and leadingsample meniscus 306 at the pipette's tip. The radial distance from thecartridge centre to the trailing sample meniscus is noted as r1; theradial distance from the cartridge centre to the leading sample meniscusis noted as r2; and the distance between the leading and trailingmenisci is noted as y, which may be described as the approximate heightof the applied sample within the transfer pipette. In other words theradial distance of the sample meniscus 305 proximate to the pipette tipshould be larger than the radial distance of the sample meniscus 306distal from the tip.

The output chamber 307 is arranged to be distal from the leading samplemeniscus. Subsequent sample processing elsewhere in the cartridge mayoccur through methods and structures connected to the outlet channel308.

In operation the transfer pipette is designed such that capillary forcesretain the sample, unless a pressure is applied to overcome them. When arotational velocity is applied by the rotary motor to generate acentrifugal force, the net flow of sample in a centrifugal microfluidiccartridge structure will always be radially outwards, i.e. from aproximal radius towards a distal radius. Therefore, once a rotationalvelocity is applied to generate a centrifugal force greater than thecapillary forces at the pipette's tip, the sample will dispense into thedistal output chamber, enabled by air displacement through the air vent309, once the condition r₂>r₁ is maintained. To maintain therelationship, r₂>r₁, the height of the applied sample within thetransfer pipette, y, should not exceed two times x (2×), where 2× isdefined by mirroring x around ℄1, always noting that ℄1 is perpendicularto the receiving chamber. A fluidic barrier 310 can be used to minimisethe risk of applied sample dispensing into the outside environment priorto application of centrifugal force through the rotary motor's rotation,or otherwise, and can also be positioned to ensure y<2×, by design.

In practice, the aforementioned parameters are dimensioned such thatonce sufficient centrifugal force is applied to overcome the capillaryforces at the tip of the transfer pipette, the sample is dispensed intothe more distal output chamber. To avoid inadvertent movement, orremoval, of the transfer pipette upon generation of centrifugal force bythe rotation of the rotary motor, a single-use locking mechanism 311 maybe used, or design variants of same.

The embodiments in the invention described with reference to thedrawings may comprise a computer apparatus and/or processes performed ina computer apparatus.

However, the invention also extends to computer programs, particularlycomputer programs stored on or in a carrier adapted to bring theinvention into practice. The program may be in the form of source code,object code, or a code intermediate source and object code, such as inpartially compiled form or in any other form suitable for use in theimplementation of the method according to the invention. The carrier maycomprise a storage medium such as ROM, e.g. CD ROM, or magneticrecording medium, e.g. a floppy disk or hard disk. The carrier may be anelectrical or optical signal which may be transmitted via an electricalor an optical cable or by radio or other means.

In the specification the terms “comprise, comprises, comprised andcomprising” or any variation thereof and the terms include, includes,included and including” or any variation thereof are considered to betotally interchangeable and they should all be afforded the widestpossible interpretation and vice versa.

The invention is not limited to the embodiments hereinbefore describedbut may be varied in both construction and detail.

The invention claimed is:
 1. A microfluidic system for processing asample, the system comprising: a transfer capillary pipette comprising asample transfer body adapted to contain the sample, said sample transferbody having a first end and a second end; and a cartridge defining alinear receiving chamber having a first end and a second end, and anoutput chamber connected to the first end of the linear receivingchamber, said linear receiving chamber configured to receive said sampletransfer body, wherein said first end of said sample transfer body ispositioned in said output chamber when the sample transfer body ispositioned within said linear receiving chamber, wherein said cartridgeis configured to rotate about a center of rotation, wherein said linearreceiving chamber is positioned non-radially with respect to said centerof rotation of said cartridge, and wherein said output chamber ispositioned closer to said center of rotation of said cartridge than saidsecond end of said linear receiving chamber is positioned to the centerof rotation of said cartridge.
 2. The microfluidic system as claimed inclaim 1 wherein the transfer capillary pipette comprises a fluidicbarrier such that when in use the distance from the fluid barrier to aleading meniscus of said sample is greater than the distance from thefluid barrier to the trailing meniscus of said sample within the saidtransfer capillary pipette.
 3. The microfluidic system as claimed inclaim 2 wherein the fluidic barrier within the transfer capillarypipette is adapted to prevent the escape of the sample through the airvent of the transfer capillary pipette.
 4. A method of processingsamples in a microfluidic system as claimed in claim 1 said methodcomprising the steps of: providing a cartridge comprising a linearreceiving chamber, the linear receiving chamber having a first end and asecond end, wherein an output chamber is connected to the first end ofthe linear receiving chamber; coupling a transfer capillary pipette tothe cartridge by inserting a sample transfer body of said transferpipette to the linear receiving chamber of said cartridge, and whereinthe sample transfer body comprises a first end and a second end, thefirst end of the sample transfer body positioned in said output chamberwhen the sample transfer body is inserted into the linear receivingchamber; and rotating the cartridge about a center of rotation such thatthe sample from the transfer capillary pipette is dispensed into anoutput chamber of the cartridge.